Reproduction in Compost Worms

It’s a bit of a maze, but hang on in there and be astounded!

The detail of reproduction in compost worms, is like the choreography of a familiar, slow dance. It just seems inevitable, somehow. The subject is discussed on every web site to do with worm farming and it is no wonder that most times it is down-played with a vague, throw-away description, such as, “when conditions are right, they pass sperm to each other,” or “the eggs meet with the sperm.”
My favourite is “mating occurs.”

I am keen on detail and to help me get my head around this complex reproduction process I found it helpful to relate the process to the compost worms’ ‘segments.’ I also have used a bit of color coding which I hope will help

Red for the male parts Blue for the female parts Green for the clitellum

3 Points to remember.

The number of segments in a worm is species specific, so there may be variations in the following, depending on which worm is being discussed. Generally, we are talking about reproduction in Eisenia Fetida.

Worms are hermaphrodites, meaning that an individual carries the sex organs of both genders, male and female. As a general rule, two worms are needed to mate, although some species, under certain circumstances, are parthenogenic, i.e. reproduction can occur without the need for a partner.(source: Edwards)

The whole process of compost worm reproduction is divided into two stages.

The transfer of sperm – done during mating and involving two worms.

The fertilisation of the eggs and the production of the cocoon – done at a later time, individually

Working Parts

Diagram showing sex organs of an earthworm

The working bit that is visible is the clitellum, the rubber-like band that you see around the worm at segments 31-37. The development of this indicates that your worm has reached sexual maturity. In E. Fetida, these will be a flushed orange colour when the worm is on heat and reproduction is imminent.

Working Parts – MALE

The bits you don’t see are, firstly, the male organs (testes) which are situated in the 10th and 11th segments. These are where sperm is produced before being channeled through the sacs to the genital opening which is situated on segment 15. It is from here that sperm is RELEASED to the partner during mating.

Segments 9 and 10 have two small openings (sperm receptacles) that RECEIVE sperm from the other worm, during reproduction.

Working Parts – FEMALE

The eggs are produced in the ovaries which are situated in segment 13 and are released into the egg sacs in segment 14.

The Process

Note the swollen, flushed clitellum. Flickr – imarsman

Mating earthworms. Flickr – Siobhan Basile

The mating compost worms approach each other nose-to-nose, slide past each other, then lie side by side with their heads at opposing ends and with the clitellum of each lying opposite segments 9-15 (location of the male parts) of the other worm. Each worm then exudes a mass of slime which encloses, or forms a connection between, the bodies of both worms from segment 9 to the end of each clitellum at segment 37. The sperm is then released from segments15 (the genital openings), moves backwards along grooves in the slime and enters the body of the partner through the two small openings (receptacles) in segments 9-10, each worm passing sperm to the other. They then depart, going their separate ways, reproduction accomplished.

Yes – the exchange is now complete and the next stage of reproduction is when the sperm meets up with and fertilises an egg(s). (This is so clever!)

The Final Stage – Fertilisation

This is the solitary part which will take place only when conditions, such as the temperature (for Eisena Fetida 15-24 degrees) are right. Indeed it could be quite some time after the mating occurred before fertilization takes place.

A new batch of mucus is exuded from the clitellum. (segments 31-37) This hardens, forming a ‘ring’ around the worm and fills with albumin. It then starts a forward movement, up the body towards the head end. Some writers say the compost worm begins to ‘wriggle out of it’. In any event, the result is that when the ‘ring’ reaches segment 14, the site of the egg-sac, it collects up a selection of mature eggs. Moving on, up the body, it reaches the sperm receptacles in segments 9-10, which, of course, now contain the previously donated sperm. The required amount of sperm (some may be saved for the future) is collected up and is now, for the first time exposed to the eggs. It is at this stage that fertilisation, finally, may take place.

To complete the reproduction process, the worm keeps wriggling backwards until the ring is sloughed off over its head, the open ends seal up and a ‘cocoon’ is born!

Worm cocoons at varying stages of maturity. (L. terrestris)

A new cocoon as it appears in your worm farm. Note lemon colour. This darkens to deep red/brown as cocoon matures.

Cocoon from Eisenia Hortensis. Thanks to RedWormComposting for use of this image.

The cocoon could stay at this stage for a very long time. Unless conditions are such that the compost worms will have a fair chance of survival, hatching will not occur. Dry conditions, for example, could hold up progress for years with the cocoons lying dormant until the moisture levels rose. (source: University of Illinois)

A few further points about reproduction in compost worms

Each cocoon probably contains around 4-6 eggs, although some writers talk in terms of 20 eggs being the upper limit. There does not seem to be a lot of support for that figure, however. Incubation is about 23 days, with the baby worm reaching adulthood from between 60-90 days and reaching full size in about one year. These little ones are compost eaters from the beginning and are particularly voracious in their ‘youth’.

Reading List.

‘The Science of Vermiculture. The Use of Earthworms in Organic Waste Management’ Edwards and Arancon